an opportunistic checkmate (the opposing player moves wrong allowing the player to mate)

versus

a forced checkmate (the opposing player will be mate regardless how the opposing player moves).

White May Mate in 2 with help from Black:

either 1.Be4 (if Black makes any move or pawn advance other than 1...Qf1+ or 1...Qh1+ (a game deciding blunder because White would simple capture the Queen with the Bishop) then White simply mates with 2.Qxh7#)

or 1.Nxf6 (if Black makes any move or pawn advance other than 1...Qxf6 or 1...Qf1+ then White simply mates with 2.Qxh7#)

White also May Mate in 3 with help from Black:

either 1.Qf7+ Kg6 (Black moves wrong allowing White to mate in 3; Black should have blocked check with 1...Bg7) 2.Be4+ Kxh5 3.g4#

or 1.Qf7+ Kxh5 (Black moves wrong allowing White to mate in 3; Black should have blocked check with 1...Bg7) 2.g4+ Kg6 3.Be4#